This invention relates to an electronic circuit for shaping a rectangular pulse into a sine-squared step shape.
Sine-squared transitions are used throughout the television industry. They appear in the T, 2T pulse and bar and the 20T and modulated 20T test signals. They are also used to shape transitions of other television test and operating pulses.
Past approaches to sine-squared shaping of television pulse rise and fall times have involved the use of multielement passive filters. In 1952, W. E. Thompson introduced, in his article "The Synthesis of a Network to Have a Sine-squared Impulse Response," Proceedings IEE (London), Vol. 99, Part III, p. 373, a method for synthesizing these filters and in 1970 A. Kastelein proposed, in his article "A New Sine-Squared Pulse and Bar Shaping Network," IEEE Transactions on Broadcasting, Vol. BC-16, No. 4, p. 84, improvements to the Thompson filter. These two approaches have been widely used in the television industry. Problems, however, have been encountered with these approaches because of their high cost and the difficulty in matching delays caused by the passive filter elements.